tonight to three people are dead including incl 8-year-old martin richard and an 29-year-old chrystal campbell ca both from massachusetts. more than 171 people werepeople injured by the blast. bl the injuries include amputated ampu limbs, and the explosives werees wer contained in pressure cookerssure and hidden in black duffle bagsduff on the ground.on t one contained shared of metal and ball bearings and the other the one had nails. n they are investigating this as an acts of terrorism but no onem bu knows who is behind it. bill brennan is for the study of of terrorism and response to terrorism also known as stars. thank you for being with hereere tonight. >> thanks for having me. >> we with what we know so far fa who do you think we're dealing with. >> i don't know. the government hasn't provided information, it may be that they don't know. kn or they're being methodical to me bring this case into the courtroom where they needeyneed evidence to stand up to the testst of thean law. la they're going to releaseing to rele information on their timetable ti but they're going to chase down every